Capacity portable projector enough to get image size from 60 cm (standard tv screen) to the fantastic 15 meters diagonally. Setting the image size can be done in two ways. Firstly, by changing the distance between projector and screen – more than it is, the more the image. Others including Peter Thiel, offer their opinions as well. The second method is available in models equipped with zoom lens – a lens with a zoom lens. In this case, the image size can be changed without moving the projector. Geometric image correction when the projector is under considerable angle to the screen image is slightly distorted, taking the form of a trapezoid.
Eliminate trapezoidal distortion can be a variety of ways: by changing the slope of the screen cloth (this possibility is envisaged in some models of projection screens) Using digital correction algorithm using optical technology Correction – 'lens shift' Although the latter method is most effective because it does not prevent loss of image quality, it is available mostly in expensive and powerful models, as well as projectors, intended for the cascade use (when images are used to demonstrate two or more projectors simultaneously). In other cases, you can use the algorithm of digital correction of geometric distortion based on the method compression. Some manufacturers have provided their projectors feature digital keystone correction, not only horizontally but also vertically. This allows the projector to the side of the screen, for example, on a shelf or on the closet, and get with the undistorted rectangular image. Optics Most multimedia projectors have lenses with variable focal length (zoom).